Explore the fundamental concept of nearsightedness in electronic matter through this 59-minute lecture by Nobel Prize laureate Walter Kohn. Delve into the theoretical foundations that underpin our understanding of how electrons behave in materials, focusing on the principle that electronic properties are primarily determined by local interactions rather than distant ones. Learn about the mathematical and physical basis for density functional theory and its applications in materials science. Discover how this nearsightedness principle enables computational approaches to studying complex materials systems and has revolutionized our ability to predict material properties from first principles. Gain insights into the theoretical framework that has become essential for modern computational materials science and quantum mechanical calculations of electronic structure.